Membrane press and work base

ABSTRACT

The invention is an improved membrane press, and method of elevating a workpiece above the supporting surface of a work base. The membrane press includes a work base having a supporting surface for carrying the workpiece, and a foil-pressing frame positioned above the workpiece for heating and applying the laminating foil to the workpiece. The improvement in the membrane press includes a plurality of workpiece-lifting pedestals residing substantially beneath the supporting surface of the work base. A piston is located beneath each pedestal, and responds to the placement of the workpiece onto the supporting surface of the work base. The piston imparts an upward force on certain ones of the pedestals residing adjacent to and beneath the workpiece to raise the pedestals and workpiece upwardly above the supporting surface of the work base. The raised pedestals permit the top surface, corners, and peripheral borders of the elevated workpiece to be laminated.

This application is a continuation of application Ser. No. 08/229,976,filed on Apr. 19, 1994, now U.S. Pat. No. 5,522,478.

TECHNICAL FIELD AND BACKGROUND OF THE INVENTION

This invention relates to a membrane press, and a method of elevating aworkpiece above the supporting surface of a work base, such as a presstable. Membrane presses have been in existence since the early 1900's,and are used for applying a uniform, laminating exterior veneer to thetop surface, corners, and peripheral borders of a relatively flat,three-dimensional workpiece. The resulting laminated workpieces aretypically used in furniture fronts, doors, cabinetry, desks, and othersimilar items where pleasing outward appearance and durability isdesirable.

The production of dome-type membrane presses for laminating a workpiecewith a veneer began in the 1930's. These type presses were effective forlaminating particularly bent or curved furniture parts. However, thelater development of a durable, wood-based MFD board, and the trendtoward furniture designs with flat surfaces and sharp edges rapidlydiminished the industry demand for dome-type presses. In response to thenew furniture trends, a new membrane press was developed incorporatingthe design of a flat press. Flat presses have larger dimensions andallow increased production. Today, dome-type membrane presses are seldomused for laminating, and are only necessary for very curved workpieces.

The pressing cycle of the present-day membrane press, using combinedcontact and convection heating, takes place in essentially four stages.The membrane press is first opened, and the laminating foil clampedalong respective edges to a tensioning frame located directly above theworkpiece to be laminated. The tensioning frame includes a top heatingplaten and membrane located adjacent to and above the laminating foil.The membrane is sucked upwardly by a vacuum source to the top heatingplaten which acts to heat the membrane.

In a second stage, the membrane press is closed over the workpiece, andthe membrane ventilated through exhaust passages. Hot air is circulatedbetween the top heating platen and membrane to further heat themembrane. The foil is sucked upwardly into contact with the heatedmembrane by a second vacuum source to plastify the foil.

Thirdly, a third vacuum source is established under the plastified foilto prevent air pockets from forming between the foil and exteriorsurface of the workpiece. The hot air circulated between the top heatingplaten and membrane is replaced by pressurized heated air to force themembrane and laminating foil downwardly onto the surface of theworkpiece.

Finally, separation air is injected between the foil and membrane tolift and separate the membrane from the foil. After pressing, any excessfoil overlapping the peripheral borders and corners of the laminatedworkpiece is removed by cutting. An addition surface finish or coatingmay then be applied to the workpiece to create a finished product readyfor use in a furniture front, or similar article.

In order to properly and uniformly apply the laminating foil to theperipheral borders and corners of the workpiece, as described above, theworkpiece must be slightly elevated above the supporting surface of thepress table. According to prior art presses, a relatively thin particleboard, often referred to as a dummy board, piggyback board, or raiserpanel, is placed under the workpiece. These dummy boards limit theproduction of the press, since the corners of the boards often crumbleduring pressing. The crumbled particles then become positioned under thefoil, which ultimately results in workpiece rejects because theparticles show through the foil. Moreover, the dummy boards must beshaped and sized to fit the dimensions of each particular workpiece.

The present invention is an alternative means for elevating a workpieceabove the supporting surface of a work press, such as a membrane press.The present invention utilizes the already-existing vacuum force actingbeneath the workpiece and foil to elevate the workpiece. This results inincreased production of the press, and reduces the number of workpiecerejects.

SUMMARY OF THE INVENTION

Therefore, it is an object of the invention to provide an improvedmembrane press which eliminates a need for dummy boards to elevate theworkpiece above the supporting surface of the press table duringpressing.

It is another object of the invention to provide a membrane pressincluding means operable for elevating any given custom-sized,three-dimensional workpiece.

It is another object of the invention to provide a membrane press havingincreased production capability.

It is another object of the invention to provide a membrane press whichproduces a reduced number of workpiece rejects.

It is another object of the invention to provide a membrane press whichincludes a workpiece elevating means responsive to the placement of theworkpiece onto the press table.

It is another object of the invention to provide a membrane press whichutilizes a pre-existing vacuum source to elevate the workpiece duringpressing.

It is another object of the invention to provide a workpiece elevatingmeans for being incorporated into any work base not limited to membranepresses.

It is another object of the invention to provide a workpiece elevatingmeans operable for elevating any given custom-sized, three-dimensionalworkpiece.

It is another object of the invention to provide a workpiece elevatingmeans for being incorporated into a work base, such as that for use inCNC routers, thermal-forming presses, deep-draw machines (vacuumpresses), or any machine combining surface and edge processing in asingle step.

These and other objects of the present invention are achieved in thepreferred embodiments disclosed below by providing an improved membranepress for applying a laminating foil to a three-dimensional workpiece tobe laminated. The membrane press includes a work base having asupporting surface for carrying the workpiece. A foil-pressing frame ispositioned above the workpiece for heating and applying the laminatingfoil to the workpiece. The improvement in the membrane press includesmeans for lifting the workpiece above the supporting surface of the workbase.

The elevating means include a plurality of workpiece-lifting pedestalsresiding substantially beneath the supporting surface of the work base.Upward movement of the pedestals results from placement of the workpieceonto the supporting surface of the work base. An upward force isimparted on certain ones of the pedestals residing adjacent to andbeneath the workpiece to raise the pedestals and workpiece upwardlyabove the supporting surface of the work base, thus permitting the topsurface, corners, and peripheral borders of the elevated workpiece to belaminated.

According to one preferred embodiment of the invention, the elevatingmeans includes a piston and cylinder located within the work base andassociated with each one of the plurality of pedestals.

According to another preferred embodiment of the invention, a source ofnegative air flow pneumatically communicates with the piston to induceupward movement of the piston within the cylinder.

According to yet another preferred embodiment of the invention, thepiston is located beneath the pedestal and cooperates with the source ofnegative air flow to urge the pedestal upwardly above the supportingsurface of the work base.

According to yet another preferred embodiment of the invention, thepiston and pedestal are connected together for pneumatically-induced,unison movement.

According to yet another preferred embodiment of the invention, the workbase includes an intake passage formed therein pneumaticallycommunicating with a rod side of the piston. The intake passagecooperates with the source of negative air flow to pneumatically induceupward movement of the piston within the cylinder.

According to yet another preferred embodiment of the invention, thepedestal defines a longitudinal bore therethrough pneumaticallycommunicating with the cylinder and intake passage of the work base. Thebore cooperates with the source of negative air flow to pull in air fromabove the supporting surface of the work base, and to move the airthrough the pedestal and intake passage. Thus, when the workpiece isloaded onto the supporting surface adjacent to and above the pedestal,air flow through the pedestal is sealed and a resulting suction forceacts on the rod side of the piston to urge the piston upwardly withinthe cylinder to lift the pedestal and workpiece above the supportingsurface of the work base.

According to yet another preferred embodiment of the invention, anexhaust passage is formed in the work base for pneumaticallycommunicating with a blind side of the piston to exhaust air from thework base after the workpiece is removed from the supporting surface andthe piston returns to its original position within the cylinder.

An embodiment of the method of elevating a three-dimensional workpieceabove the supporting surface of a work base according to the inventionincludes the steps of first loading the workpiece to be elevated ontothe supporting surface of the work base. After loading, the workpiece ispneumatically lifted above the supporting surface of the work base bymeans responsive to the placement of the workpiece onto the supportingsurface of the work base.

A second embodiment of the method of elevating a three-dimensionalworkpiece above the supporting surface of a work base having a pluralityof top-surface openings therein communicating with a plurality ofcylinders for receiving and housing a plurality of workpiece-liftingpedestals positioned within the cylinders for movement between aworkpiece-loading position and a workpiece-laminating position above thesupporting surface of the work base includes the step of loading theworkpiece to be elevated onto the supporting surface of the work base. Asecond step includes lifting those pedestals covered by the workpieceupwardly from the workpiece-loading position to the workpiece-laminatingposition in response to placement of the workpiece onto the supportingsurface of the work base to thereby elevate the workpiece above thesupporting surface of the work base.

According to another preferred embodiment of the invention, the methodfurther includes the step of directing a flow of air from above thesupporting surface of the work base, through the pedestal, and throughan intake passage formed in the work base. Thus, blocking air flowthrough the pedestal creates negative air pressure acting on thepedestal to lift the pedestal upwardly above the supporting surface ofthe work base.

According to yet another preferred embodiment of the invention, themethod further includes the step of locating a piston within each of thecylinders for cooperating with the air flow for pneumatically-inducedupward movement of the piston and the pedestal within the cylinder.

According to yet another preferred embodiment of the invention, the stepof locating a piston within each of the cylinders further includes thestep of connecting the piston to a bottom end of the pedestal forpneumatically-induced, unison movement of the piston and the pedestal.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the objects of the invention have been set forth above. Otherobjects and advantages of the invention will appear as the inventionproceeds when taken in conjunction with the following drawings, inwhich:

FIG. 1 is a front elevation of a membrane press according to the priorart showing various elements in cross-section, and showing the membranepress in an open position prior to pressing;

FIG. 2 is a front elevation of the membrane press illustrated in FIG. 1showing various elements in cross-section, and showing the membranepress in a closed position during pressing;

FIG. 3 is a front elevation of a membrane press according to the presentinvention showing various elements in cross-section, and showing themembrane press in an open position prior to pressing;

FIG. 4 is a fragmentary, enlarged, cross-sectional view of a singlepedestal, piston, and cylinder according to the workpiece elevatingmeans and membrane press of the present invention, and showing thepedestal in a workpiece-loading position within the cylinder;

FIG. 5 is a fragmentary, top plan view of the work base according to theworkpiece elevating means and membrane press of the present invention;

FIG. 6 is a fragmentary, enlarged, cross-sectional view of a singlepedestal, piston, and cylinder showing the relative positions of thepedestal, piston, and workpiece immediately after placement of theworkpiece onto the work base, and just prior to upward movement of thepiston within the cylinder; and

FIG. 7 is a fragmentary, enlarged, cross-sectional view of a singlepedestal, piston, and cylinder showing the relative positions of thepedestal, piston, and workpiece after placement of the workpiece ontothe work base, and showing the pedestal in a workpiece-laminatingposition above the supporting surface of the work base.

DESCRIPTION OF THE PREFERRED EMBODIMENT AND BEST MODE

Referring now specifically to the drawings, a membrane press accordingto one prior art embodiment is illustrated in FIG. 1 and shown generallyat reference numeral 10. The membrane press 10 is used for applying alaminating foil 11, such as polyolefine, to the exterior surface of aworkpiece 15 to be laminated. Preferably, the workpiece 15 is awood-based, profiled MFD board. Such boards are typically used asfurniture fronts for cabinetry, countertops, kitchen tables, and thelike.

As shown in FIG. 1, the prior art membrane press 10 includes a work base20 for supporting the workpiece 15 to laminated. The work base 20 isconstructed generally of a bottom press table 21 and bottom heatingplaten 22. A vacuum or suction force, generated by a turbine 25,communicates with the work base 20 through air passages 26 defined inthe work base 20 to eliminate trapped air or air pockets which may formbetween the workpiece 15 and laminating foil 11 as the laminating foil11 is heated and applied to the top surface, edges, and borders of theworkpiece 15.

A top heating platen 31, membrane 32, and tensioning frame 33 arepositioned above the workpiece 15 for heating the laminating foil 11,and applying the laminating foil 11 to the workpiece 15. According toprior art presses, in order to properly laminate the edges andperipheral borders of the workpiece 15, a dummy board 35 is placed underthe workpiece 15 to slightly elevate the workpiece 15 above thesupporting surface 20A of the work base 20. By elevating the workpiece15, the press 10 can properly and uniformly apply the laminating foil 11to the peripheral borders and contours of the workpiece 15.

As shown in FIG. 2, the tensioning frame 33 is lowered onto thesupporting surface 20A to apply the heated, plastified foil 11 to theelevated workpiece 15. As discussed above, the suction force created bythe turbine 25 serves to eliminate air pockets which may form betweenthe workpiece 15 and laminating foil 11 as the laminating foil 11 isheated and applied to the top surface, edges, and borders of theworkpiece 15.

MEMBRANE PRESS OF THE PRESENT INVENTION

As shown in FIG. 3, the present membrane press 50 includes many of thesame elements of the prior art membrane press 10 described above andillustrated in FIGS. 1 and 2. Like elements referenced in FIGS. 3-7 areindicated in prime notation. In alternative embodiments (not shown), themembrane press 50 may utilize any desired foil-pressing frame known inthe art, such as a Vario-frame or multi-purpose frame. In addition, thepresent membrane press 50 is not limited to a particular class ofpresses. For example, the membrane press 50 may be one which ispreferably operated without a membrane, or one which is preferablyoperated with a membrane, or one which must include a membrane.

The membrane press 50 preferably includes a work base 60 having a flatsupporting surface 60A for carrying the workpiece 15' to be laminated.Preferably, the work base 60 includes a press table 61 supported bylegs, and bottom heating platen 62. During pressing, the bottom heatingplaten 62 serves to further heat the laminating foil 11' as the foil 11'is applied to the workpiece 15'.

As is generally known in the art, membrane pressing occurs by clampingthe edges of the laminating foil 11' into the foil-pressing frame 33',heating the foil 11' by operation of the top heating platen 31' andmembrane 32', and then lowering the foil-pressing frame 33' onto thesupporting surface 60A to uniformly apply the foil 11' to the workpiece15'. When the laminating foil 11' is applied to the workpiece 15', theworkpiece 15' must be sufficiently elevated above the supporting surface60A of the work base 60 to allow proper and uniform application of thefoil 11' to the corners, edges, and borders of the workpiece 15'.Preferably, the workpiece 15' is elevated approximately 15-20 mm abovethe supporting surface 60A during pressing.

One prior art means of elevating the workpiece 15' includes using adummy board 35, as described above and shown in FIGS. 1 and 2. Thepresent membrane press 50 eliminates the use of a dummy board, andinstead, utilizes pneumatic elevating means responsive to the placementof the workpiece 15' onto the supporting surface 60A of the work base60. The elevating means of the membrane press 50 is described in detailbelow.

WORKPIECE ELEVATING MEANS

Referring now to FIGS. 3-7, the work base 60 of the membrane press 50includes a plurality of top-surface openings 71 and cylinders 72 formedtherein for receiving and housing a plurality of workpiece-liftingpedestals 75. Preferably, prior to loading the workpiece 15' onto thework base 60, approximately 50-100 percent of the length of eachpedestal 75 remains positioned within the cylinders 72 beneath thesupporting surface 60A of the base 60.

As best shown in FIGS. 4, 6, and 7, each pedestal 75 includes alongitudinal bore 76 therethrough for pneumatically communicating withan air intake passage 78 formed in the press table 61 and bottom heatingplaten 62 of the work base 60. As indicated by direction arrows in FIG.4, a turbine 80 creates a negative air flow through the pedestal 75,cylinder 72, and intake passage 78 to suck in air from above theworkpiece supporting surface 60A.

A piston 81 is connected to a bottom end of each pedestal 75, andcooperates with the negative air flow for impartingpneumatically-induced upward movement of the piston 81 within thecylinder 72. As discussed in detail below, the upward movement of thepiston 81 and pedestal 75 is dictated by the free, unobstructed flow ofair from above the supporting surface 60A through the pedestal 75,cylinder 72, and intake passage 78.

Referring now to FIGS. 6 and 7, upward movement of the pedestals 75 andthe resulting elevation of the workpiece 15' in response to placement ofthe workpiece 15' onto the supporting surface 60A of the work base 60 isshown. FIG. 6 illustrates the position of the piston 81, pedestal 75,and workpiece 15' immediately after placement of the workpiece 15' ontothe supporting surface 60A of the work base 60, and just prior to upwardmovement of the piston 81 within the cylinder 72. The workpiece 15'obstructs and seals air flow from above the supporting surface 60Athrough the pedestal 75. As a result, the negative air flow generated bythe turbine 80 creates a vacuum in the cylinder 72 which produces asuction force on the rod side of the piston 81 to lift the piston 81upwardly within the cylinder 72. Preferably, the turbine 80 generates anupward force on the piston 81 of approximately -0.7 to -0.9 bar.

As shown in FIG. 7, once the workpiece 15' has been loaded onto thesupporting surface 60A, air flow through the pedestal 75 is blocked, andthe resulting suction force acting on the piston 81 operates to lift thepiston 81 and pedestal 75 upwardly. The upward movement of the pedestal75 elevates the workpiece 15' above the supporting surface 60A asufficient height and with sufficient force to permit the top surface,edges, and peripheral borders of the workpiece 15' to be properlylaminated in the membrane press 50. The pedestals 75 not covered by theworkpiece 15' remain positioned within the cylinders 72 and do noteffect pressing of the workpiece 15'.

When the workpiece 15' is removed from the work base 60 after pressing,air flow through each pedestal 75 is unobstructed, and the respectivepistons 81 and pedestals 75 return to their original positions withinthe cylinders 72, as shown in FIG. 4. Air is preferably exhausted fromthe cylinder 72 through an exhaust passage 82 formed in the heatingplaten 62 and press table 61.

Application of the workpiece elevating means described above inconnection with the membrane press 50 is not limited to membranepresses. Rather, the elevating means may be applied to any structurehaving a supporting surface for carrying a workpiece to be elevated. Forexample, the workpiece elevating means and method may be incorporatedfor use in CNC routers, thermal-forming presses, deep-draw machines(vacuum presses), or any machine combining surface and edge processingin a single step.

An improved membrane press and method of elevating a workpiece above asupporting surface is described above. Various details of the inventionmay be changed without departing from its scope. Furthermore, theforegoing description of the preferred embodiment of the invention andthe best mode for practicing the invention are provided for the purposeof illustration only and not for the purpose of limitation--theinvention being defined by the claims.

I claim:
 1. In a membrane press for applying a laminating foil to athree-dimensional workpiece to be laminated, the membrane pressincluding a work base having a substantially flat supporting surface forcarrying said workpiece, and a foil-pressing frame positioned above saidworkpiece for heating and applying the laminating foil to saidworkpiece, the improvement in said membrane press comprising:(a) aplurality of workpiece-lifting pedestals positioned for movement betweena workpiece-loading position recessed within said work base, and aworkpiece-laminating position extending above the supporting surface ofsaid work base; and (b) elevating means automatically responsive to theplacement of said workpiece onto the supporting surface of said workbase to cover at least one of said pedestals, and for lifting those ofsaid pedestals covered by said workpiece upwardly from theworkpiece-loading position to the workpiece-laminating position, therebyelevating the workpiece supported on those of said pedestals forpermitting the top surface, corners, and peripheral borders of theelevated workpiece to be laminated.